The very first model of the celebrated Daytona series was the reference 6239, and was seen in sales catalogues in Europe as of 1964. Reference 6239 was the firm's first chronograph with the tachometer scale on the bezel, whereas previous models, such as the reference 6238, had it printed on the dial. Another notable difference was that the subsidiary dials were printed in a different color than the main dial for better readability. Early models featured only the designation Cosmograph on the dial, and Daytona was added on later series to mark Rolex's sponsorship of the renowned NASCAR stock car race.
Reference 6241 was introduced into the market in the early 1960s and remained in production until around 1969. Available in stainless steel, 14K and 18K gold, it was fitted with the non-Oyster or non-screw down chronograph buttons and a bezel with black plastic insert, the tachymetre scale printed in white.
The so-called exotic or tropical dials, were later called Paul Newman dials, so named after the actor was photographed wearing a reference 6239 Daytona in a publicity shoot for the film Winning.
Examples of the reference 6241 are described and illustrated in I Cronografi Rolex - La Leggenda, Pucci Papaleo Editore, pp. 312-319, and 100 Superlative Rolex Watches by John Goldberger, pp. 238-261.